In conventional printed circuit boards manufactured currently there are typically numerous electronic components secured to a dielectric or insulating substrate. Each electronic component typically includes a plurality of leads which must be soldered to conductive pads carried on the dielectric substrate.
Current technology for mounting electronic devices or components on printed circuit boards is commonly referred to as surface mount technology. In this technique the components are mounted to solder pads on one or both faces of the printed circuit board. Such technology allows higher density packing of electronic components on a circuit board than is possible using other mounting technology such as through-hole lead mounting.
The types of leads on integrated circuit chips which are commonly used in surface mounting are J-leads and gull wing leads. These types of leads extend downwardly from the side or underside of the electronic component and are simply soldered to a connection pad on the same side of the board on which the electronic component is mounted. Use of the J-leads is especially advantageous because they require less space than other types of leads by reason of the fact that the solder pad is physically located beneath the component. However, gull wing leads are easier to inspect and repair.
Unfortunately, the higher density packing of electronic components on a printed circuit board renders it difficult to adequately inspect the quality of solder joints or bonds between the leads of the electronic component and the pad on the printed circuit board. Because of the very close spacing of the electronic components, it is difficult to visually inspect under or between the components to determine whether all leads have been soldered, or whether any solder fillets or joints have cracked or failed.
Although printed circuit boards can be tested electronically to determine whether there are any defects, this is time consuming, expensive, and not totally accurate. Furthermore, it is still necessary to inspect or test individual fillets or joints to verify that proper electrical connections have been made.
It is possible to inspect J-lead connections by tilting the printed circuit board on edge and then visually examining the connections using a large microscope. However, this is a an awkward and very tedious procedure, and some solder joints are visually obscured by adjacent tall components. Also, many incorrect or defective J-lead solder joints cannot be visually observed from directly above a component on the board.
By increasing the spacing between electronic components on the printed circuit board it is easier to visually inspect the connections. However, this defeats the purpose of using J-leads to allow close spacing of components.
There has not heretofore been provided a hand-held, portable, visual inspection aid which is suitable for inspecting connections on printed circuit boards where electronic components are closely spaced.